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New here and new rx8 owner. Read through most of the stickys before buying. Very good information there. I'm just a bit confused about the use of premix. From what I gather these engines don't like synthetic. I believe the previous owner was using 5w20 as per manufacturer recommendations. That being said the Idamitsu and other high quality 2 stroke oil I've been looking into is synthetic. So is it alright for premix but not for your regular engine oil? Ive come to the conclusion premixing is a good idea, I just don't want to use the wrong stuff. I've been looking at using Castrol activ 2 stroke motorcycle oil. Will this work? Also I should mention my OMP is still hooked up. And just one more thing will premixing cause your cat to clog?
Even with engine oil, people have been using synthetic for a while with no ill effects, and 5W20 is fine unless you live somewhere very hot. Use whatever you think will work from your research and change regularly. The latter is the key.
Synthetic 2-stroke is not an issue. In fact, most of the common 2-stroke oils are synthetic. I haven't seen anyone reporting any issues with most reputable premixes.
Premix and oil can be a bit hard on the front O2, but shouldn't cause too much of a problem for the cat. If you are worried, look for a good aftermarket cat, or decat if you are okay with the consequences.
There are a gazillion posts on this, and almost as many opinions.
Mazda uses synthetic oil in Japan, but they don't recommend it in the U.S., probably because of MPG.
I've been using Mobil1 0W40 for 5 years and about 60k miles, premixing usually with Lucas semi-syn because It's convenient, but any JASO certified is acceptable.
Do some research and decide for yourself.
As others have said - and will say - the important thing here is to check oil level often (every other fill-up) and to change it regularly. It seems cars with ordinary engines are relatively forgiving regarding oil level (it's not the end of the world if oil is not topped up) or delayed oil changes (you skip an oil change or wait an extra few months and it's no big deal), but casual oil maintenance like that is not good for the Renesis. I believe the rotary engine simply has a smaller "margin of error" for owner neglect.
Premix vs no premix, dino vs synth, and oil weight are not nearly as important as keeping the oil level from 3/4 to full and changing it on schedule. Hope this helps.